1. Field of the Invention
The present invention relates to a thin-walled ceramic honeycombed elongated catalyst carrier which is to be provided with a suitable catalyst particularly for removing nitrogen oxides from flue gases from industrial power and heating plants.
The present invention also relates to a method for the production of an elongated honeycombed ceramic catalyst carrier with a selected high porosity of the ceramic material and low flow resistance for the waste gases or other fluids to be treated.
2. Description of Prior Art
In the British Patent Specification No. 1 402 206 corresponding to German Specification No. 22 10 438 a ceramic catalyst carrier is described which has parallel passages or channels for fluids. The ground mass of aluminium oxide and/or magnesium oxide and/or titanium dioxide and/or activated alum earth and/or quartz comprises up to 10% graphite as opening material which results in secondary pores when the structure is fired. About 30 channels per square centimeter or more are formed by pressing pins into a compressed block of green material giving a total open cross-sectional area ranging from 30 to 50% of the total cross-sectional area, and a total porosity of up to 60% is expected. However, because of the low open cross-sectional area of the channels and their very small diameters these ceramic catalyst carriers show a high flow resistance and the channels may be blocked by particles in a flue gas so that there is no advantage from the porosity.
In the German Patent Specification No. DE-PS 26 58 539 (corresponding to U.S. Pat. No. 4,358,428 of Fujita et al.) a honeycomb-shaped catalyst for removing of nitrogen oxides is proposed having a total open cross-sectional area ranging from 50 to 80% of the total cross-sectional area. According to an example the catalyst consists of a cordierite-ceramic structure. Obviously no secondary porosity for an enlarged surface area of catalyst is used here. Further in the German Patent Specification No. DE-PS 3 046 921 square structures of not specified material having square channels are combined to a bundle.
Another honeycombed catalyst carrier with a plurality of channels of preferably circular cross-section made by extrusion from a ceramic material such as cordierite is known from published German Patent Application No. DE-OS 2 421 311 (corresponding to U.S. Pat. No. 3,930,522 of C. L. Turner). However, here again the channels have a narrow diameter and the total open cross-sectional area of this structure is less than 55% of the total cross-sectional area.